High-potential fuse



Oct. 8, 1929.

A. O. AUSTIN HIGH POTENTIAL FUSE Fly 1 m M m v a .w m 4 R @wrw v S F u INVENTOR. MM 0 m m /61M ATTORNEYS Oct. 8, 1929; 0, AUSTIN 1,730,716

HIGH POTENTIAL FUSE Filed May 25, 1925 4 Sheets-Sheet 2 Oct. 8, 1929. A. o. AUSTIN HIGH POTENTIAL FUSE Filed May 25, 1925 4 Sheets-Sheet 3 I N VEN TOR.

A TTORNEYJ Oct. 8, 1929. A. o. AUSTIN 1,730,716

HIGH POTENTIAL FUSE Filed May 25, 1925 4 Sheets-Sheet 4 A TTQRNEYS I Patented Oct. 8, 1929 UNITED STATES PATENT OFFICE ARTHUR 0. AUSTIN, OF BABBERTON, OHIO, ASSIGNOR, BY MESNE ASSIGNMENTS, TO THE OHIO BRASS COMPANY, OF MANSFIELD, OHIO, A- COBPOBATION OF NEW JERSEY HIGH-POTENTIAL FUSE Application filed May 85, 1925. Serial No. 82,710.

This invention relates to means for protecting fuse wires used in high potential circuits from the destructive effect of discharge and for minimizing the tendencyto are across when such circuits are broken. The object of the invention is to provide means for controlling the electrostatic field adjacent the circuit breaker in a high potential circuit, to minimize arcing when the circuit is broken, and to prevent the injurious effect of corona or streamers emanating from a fuse wire. i

The invention is exemplified in the combination and arrangement of parts shown in the accompanying drawings and described in the following specifications and it is more particularly pointed out in the appended claims.

In the drawings- Fig. 1 is a sectional view of a fuse member having one embodiment of the present invention applied thereto.

Figs. 2, 3, 4, 5 and 6 are views similar to Fig. 1 showing different forms of the invention.

Fig. 7 is a transverse section on line 77 of Fig. 6. i

Fig. 8 is a part elevation and part section of another modification of the invention.

In fuses used for protecting electrical apparatus or for disconnecting electrical circuits in case of overload, little difficulty is found until it is desired to use the fuses on electrical circuits operating at high voltages. It is to provide an improved fuse for high voltage circuits that this invention is especially applicable.

In general, there is danger of a discharge between the ends of high voltage fuses owing to too high a stress in the air at the terminals or conducting surfaces. This difiiculty may be overcome to a very lar e extent by the use of an insulated control or preventing discharge. There is another difiiculty in that where an ordinary fuse is used which has a small fuse wire or element, the electrical discharge from the surface due to the formation of corona or streamers produces oxides and nitrates or other compounds which will destroy the fuse in a comparatively short time. This difficulty may be prevented by the application of the present invention.

In the form of the invention shown in Fig. 1, a fuse 10, terminating at bolts or clips 11, runs through an insulating tube 12. The insulating tube is equipped with terminal members 13 with clips or tongues 14. In high voltages the current is usually small so that the fuse 10 will necessarily be of small diameter. The stress in the surrounding air at high voltage will then cause a discharge so that the fuse maybe destroyed or its current capacity altered in a comparatively short time. If, however, the fuse is shielded by insulated controls 15 there may be little or no discharge from the fuse although of small size. The insulated control is described more fully in previous Patent No. 1,521,743. The insulated control not only raises the flash-over voltage for a given distance between the terminals of the fuse tube, but also has the further advantage in that the discharge from the fuse owin to the small diameter and high voltage may e reduced or prevented. This makes it possible to use fuses of much shorter length and much smaller diameter, and at much higher voltages.

It is evident that when the fuse blows there will be a difference of potential between the ends and there is likely to be a discharge owing to high concentration of stress in the air at one or both of the terminals. The insulated control relieves this stress and tends to prevent the are from picking up after the fuse is blown. It is evident that the insulated control in this case acts so as to control the discharge between the two surfaces.

The body of the fuse tube 12 may be provided with water sheds 16 of suitable desi for the purpose. The space within the tu e surrounding the fuse may be filled with suitable packing 17 such as asbestos, marble dust or ot er suitable material.

Another form of the invention is shown in Fig. 2. The fuse tube 18 containing the fuse 10 is equipped with insulated controls 19 of a flange or circular type; These aremade large so as to control the electrostatic field and protect the fuse from serious discharge. They also serve the purpose of shielding siderable distance out, raising rough parts at the ends of the fuse so that the will not discharge.

Fig. 3 shows another modification of the invention for preventing high flash-overs and protecting fuse tubes from destruction owing to too. igh an electrical stress in the surrounding air. It is evident that the invention may be applied equally well to other types of fuses such as spring fuses or fuses operatin in an insulating medium such as o1lor ot er suitable material. InFig. 3 a main fuse tube 20 has a liner 21. It is sometimes advisable to have an additional inner liner made of porcelain, glass or other refractory material as shown at in Fig. 6. The liner or tube 21 may be made of fibre or other suitable material which is not fragile so that accidental breaking due to heat or explosion will not cause the fuse to collapse as a whole. The member 20 is provided with charged surfaces 23. These control the electrostatic field at the ends and for a conthe flash-over for a given length of fuse tu e as explained in the previous patent referred. to above. Where it is desired to make the fuse tube long, the pockets 23 may have to be extended too far alon the tube or there may not be sufficient electric strength between the adjacent ends of the surfaces 23. In order to I provide suflicient dielectric strength and still control the electrostatic field around the fuse, additional conducting members 24 are used. These members are so arranged that they form electrostatic condensers between the charged surface 23 and the adjacent surface of the member 24. Owing to the condenser I action between the two, the surface adjacent vantage in preventin the fuse tube at the inner extremity of the member 24 is controlled so as to protect the fuse from discharge. The conducting members-24 are covered by an outer dielectric tube 25 which ma be molded upon the outer surface of the tu e 20.

Other methods of shielding the fuse so that it will not be destroyed by acids or compounds formed by electrical discharge are shown in Figs. 4, 5 and 6. In most cases the electrostatic shielding ma also be used for increasing the arcing vo tage between the terminals of the fuse, which is of great adre-establishment of an are once a fuse is lown. This may be accomplished by an external electrostatic shield or insulated control or an internal shield system as shown in Figs. 4, 5, and 6.

In Fig. 4 the electrostatic members 30, 31, 32, 33 and 34 are embedded inthe insulation which may be a molded composition. The end screens 30 and 34 are connected to the clips 36 at the end ofthe fuse tube. The shields or screens 30 and 34, the fuse 37, and the clips 36 are all in electrical contact. The mutual electrostatic capacity between 30-, 31, 32, 33 and 34 may be so proportioned that an path adjacent to the shields. The main part of the electrostatic field adjacent the center portion of the fuse will be set up by the conenser or electrostatic couplingbetween the several members 30, 31, 32, 33 and 34.

In Fig. 5, the general arrangement is somewhat the same except that the electrostatic shields at the ends are placed on the outside. The ones in the center are nearest the fuse. The two types involve difi'erent manufacturing problems, and one ty e may have particular advantage over the ot er one depending on surroundin field conditions. In Figs. 4 and 5 the mem ers' may be made up with the electrostatic shields embedded in a layer 38 of a separate dielectric member 39 inserted in the inside. This latter member may be porcelain, glass or a different composition which has the advantage of greater mechanical reliability or less tendency to carbonize or the fuse may be mounted in a small porcelain or glass tube inside of the member 39 as shown in 40 in Fig. 6.

In Fig. 6 the dielectric member 41 has screen surfaces or electrodes 42 projecting from opposite ends and electrically connecte to thecaps 43 which in turn are electrically connected with fuse 37 and clips 36. The electrodes 42 projectin from opposite ends are relatively offset an do not intersect but overlap. These members being in electrical contact with the fuse are at the same potential and being outside of the fuse they reduce the electrical stress or gradient on the fuse tending to cause discharge from same. The elec- Y trodes bein covered with insulation also act as insulate flux controls so that the tendency for arcing between the ends after the fuse is blown is reduced, particularly for high frequency conditions. It is not necessary to place solid electrodes 42 in an insulating material but it is evident that these may simply consist of openings with metallized surfaces or filled with conducting material. The electrodes or screen surfaces 42 may be located in an outer member 41 which may be of uniform cross section or the cross section may be so designed as to provide the necessary dielectric strength. In order to insure mechanical reliability where the member 41 may be of fragile material such as glass or other material, an insulating non-fragile member 14 Ill It, 'of couree, is evident that fuses may be screened by any suitable electrostatic screen at the end. One of these is shown in Fig. 8. The insulating member 45 has electrostatic members 46 attached to. the end caps 43 by arms 47. The electrostatic members pro'ecting well out in the field, screen the fuse mm the electrostatic field tending to cause discharge with consequent destruction of the fuse. The shields may be of any suitable form and it may be so made as to act as a water shed to keep a portion of the fuse tube dry. Instead of arms 47, the surface 48 is closed, acting as a water shed. It is evident that the whole end piece may be made in one or a number of parts without changing the result.

I claim 1. The combination with a circuit breaker for a high potential circuit of a flux control member comp'risin an element of conducting material electrical y connected with said circuit breaker at each side of the point at which the circuit is,broken, and solid dielectric covering for said elements disposed at the sides thereof between said elements, the space between said flux control members being less than the length of the gap formed by said circuit breaker when opened.

2. The combination with a fuse wire for a high potential circuit of a flux control member comprising an electrode connected with said circuit at each end of said fuse wire, and extending in the direction of said fuse, but spaced outwardly therefrom, the distance between adjacent ends of said electrodes being less than the length of said fuse wire and solid dielectric covering for said electrodes interposed therebetween.

3. The combination with a fuse for breaking a high potential circuit of a tubular member of dielectric material enclosing said fuse, and a flux control member connected with said circuit and extending inthe direction of said fuse outside of said dielectric tubular member to a point opposite a portion of said fuse between the ends thereof, said flux control member having means on the extreme portion thereof for reducing the tendgie cy for electrical discharge from said memr. 4. The combintion with a fuse wire for a high potential circuit of terminal members.

a screen to minimize discharge from said wire, and a dielectric covering for said conductor member.

6.- The combination with a fuse wire for high potential circuits of terminals connected with the ends of said fuse wire, conductor members connected with said terminals and extendin' toward each other in the direction of said use wire to points intermediate the ends of said wire but spaced outwardly there from and serving as electrostatic screens to minimize electrical discharge from said fuse wire, and coverings of dielectric material for said conductor members.

7. The combination with a fuse wire for high potential circuits of a dielectric tube enclosing said fuse wire, terminals for said fuse wire at opposite ends of said tube, conductor members connected with said terminals and disposed adjacent portions of said fuse wire between the ends thereof but spaced therefrom, and coverings of dielectric material for said conductor members.

8. The combination with a fuse wire for high potential circuits of terminals connected to opposite ends of said fuse wire, a tubular member of dielectric material inter osed between said terminals and surroun ing said fuse wire, flux control horns connected with said terminals and disposed outside of said tubular member, and coverin s of dielectric material for the ends of said orns.

9. The combination with an overload device for breaking a high potential electric circuit of insulated flux control members connected to said circuit at opposite sides of said overload device and disposed opposite a point between the ends of the gap formed when said circuit is broken, but spaced therefrom to minimize arcing when said circuit is broken, each of said flux control members comprising a member of conducting material having the portion thereof directed toward the other flux control member embedded in solid dielectric material. V

10. The combination with a fuse wire arranged to serve as an overload device for breaking a high potential circuit, of insulation covered flux control members connected with said circuit at the ends of said fuse Wire, extending adjacent to said fuse wire and spaced therefrom and operating to prevent discharge from said fuse wire while said fuse wire is intact and serving as flux control members to minimizearcing when said circuit is broken, each of said flux control members comprising a member of conducting material having the portion thereof directed toward the other flux control member embedded in solid dielectric material.

11. The combination with a fuse wire of terminal members connected to opposite ends of said fuse wire, a tube of dielectric material connecting said terminal members and ends but separated therefrom and serving as use surrounding said fuse wire and a flux control member connected with one of said termmal members and extending toward the other of said terminal members outside of said dielectric tube to a point closer to said other termiv nal member than the end of said fuse wire secured to the terminal member with which said flux control member is connected, said flux control member comprising a memberof conducting material,' a dielectric covering therefor interposed between said member of conducting material and the said terminal member toward which said member of conducting material extends.

12. The combination with a fuse wire of a dielectric tube enclosing said fuse wire, terminal members supported on the opposite ends of said tube and connected with the opposite ends of said fuse wire respectively and flux control members connected with said terminal members and extending toward the central portion of said tube but outside thereof, the extremites of said flux control member being covered with dielectric material.

13. The combination with a circuit breaker for a high potential circuit, of a flux control member comprising an element of conducting material electrically connected with said circuit breaker at one side of the gap formed by said circuit breaker when open and directe toward the other side of said gap, and solid dielectric covering disposed about the portion of said element nearest said other side of said gap, the space between said flux control member and said other side of said gap being less than the gap between the poles of said circuit breaker when open. v

In testimony whereof I have signed my name to this specification on this 19th day of May, A. D. 1925.

ARTHUR O. AUSTIN. 

